Signaling system



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P. B. MURPHY SIGNALING SYSTEM Filed Aug. 6. 1924 8 Sheets-Sheet 3 Dec. 1, 19 25.

P. B. MURPHY SIGNALING SYSTEM Filed Aug, 6. 1924 8 Sheets-Sheet 5 Dec. 1,1925. 1,563,517

P. B. MURPHY SIGNALING SYSTEM Filed Aug. 6, 1924 8 Sheets-Sheet 6 all I. 0 v 4 hue/7mm- Paa/ 5. harp/I P. B. MURPHY SIGNALING SYSTEM 41 5- 1924. s Sheets-Sheet '1 Wye/flan Pay/5. M0500 I Dec. 1, 1925.

P. B. MURPHY SIGNALING SYSTEM Filed Aug. 6. 1 8Sheets-Sheet 8 /m/emorr Pall/15! Mam/2y Patented Dec. 1, 1925,

1,563,517 UNITED STATES PATENT o Frcn'f PAUL B. MURPHY, OF NYACK, NEVI YORK, ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

. SIGNALING SYSTEM.

Application filed August 6, 1924. Serial No. 730,366.

To all whom it may concern:

Be it known that 1, PAUL 1%. MURPHY, a citizen of the United States of America, residing at Nyack, in the county of Rockland and State of New York, have invented certain new and useful Improvements in Signaling Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to signaling systems, and more particularly, to improved methods and means for signaling over transmission lines.

Under the present telephone practice involving the use of toll lines inter-connect .ing di'fierent exchanges, several methods of extending calls are employed. For example, in. case a toll. connection is to be extended automatically and can only be completed between two exchanges through-one or more intermediate exchanges, the toll operator at the originating exchange must,- at'tcr having connected manually to a toll line leading to the first intermediate exchange, set up the remainder of the connection by dialing one portion at a time oi. the toll code number representing the desired exchange, each portion representing an autonmtically established connection to a. succeeding exchange, each succeeding portion being dialed only after the operator has received a signal to proceed. Thus, the speed of setting up a connection depends to a large extent on the individual operator s skill in attention to signals and her knowledge of the routes by which the distant exchange may be reached.

it is an object of this invention to eliminate the necessity tor the toll operator to dial the toll code number in sections or know the route to be employed by atoll connection between two exchanges and to this end means is provided whereby the toll operator may establish a toll connection to a distant exchange by merely dialing once the complete toll code number, regardless of how many intermediate .ex changes may be involved or what route is to be followed, and without having to pay any attention to any signals during the establishing'ot the connection.

Anotherobiect is to provide means whereby all dialing impulses and supervisory or controllingsignals incidental to the establishi'ng otajto ll connection;may b as far as signals between exchanges that over the toll lines are concerned, of a high frequency alternating current character. By employing this type of impulses it is ii'nmaterial what kind of toll lines are used in this system for example, ordinary wire toll lines with or without repeater equipments, a channel of a carrier telephone installation, a radio telephone connection, composite lines or phantom lines may be equally well employed without fear of any disturbing eitects from the toll line signalmg.

To obtain these objects according to one change available to any toll operator in that exchange for selecting an idle toll line extending in the general'direction of the desired exchange, that is, an idle switching equipment may be selected and directively operated to select, hunt for and connect to an idle toll line in any one of a number of groups of toll lines over which the desired exchange may be reached.

Another feature of the invention is the provision of means in connection with said common switching equipments whereby the toll operator may selectively operate other local automatic switches at the exchange to connect directly with a subscribers line in the exchange.

Another feature of the invention is the provision of means in connection with said common switching equipments, whereby high frequency signaling impulses incoming over toll lines terminating at an exchange may be utilized to select an idle outgoing toll line in any one of a number of groups of toll lines over which a distant exchange may be reached and whereby such. incoming signaling impulses may also be utilized for the operation of other local switches to select a desired subscriber s line in the originating exchange it the call is not intended to go beyond this exchange.

feature of the invention automatic switchmg equipments are provided at each ex-' Another feature of the invention tl the distant exchange-over the-selectechoutgoing t oll-line',-said= appropriated sender is operated to transmit the toll code number over said tollline.

Another featureis the provision, in the sender equipments, of ordinary dialing mechanisms of the type used by operators or subscribers in producing dialing impulses equipped with means for automatic manipulation by incoming impulses to store such impulses and automatic manipulation to transmit impulses.

Another feature'o'f the invention is the provision of cord'circuits for the use'of the toll operators "by means of which both high frequency alternating current and direct current dialing impulses'may be transniitted simultaneously to an automatic switching equipment taken for use and by'mea'ns of which high frequency current signals na'y be transmitted to or receivedlrom a selected outgoing toll line for supervisory purposes during the establishing and release of the toll lineconnections;

Another feature of the invention is the provision of means whereby the direct current impulses representing a tollicoflde number received from a cord circuitof the above typeinay' be utilized for: the selecting operations of. an idle outgoing toll line" andIfori assoc; ated thereon; for translating the' released direct current impulses constituting said number into high frequency alternatingv current impulses, and transmitting saidimpuls'esover a selected idle outgoing tollline;

Another feature of the' invention is the provision of means in connection with an automatic switching equipment and sender taken for use for translating. high frequency" alternating current signaling impulses receivecl over an incoming .tollline into direct current impulses, and means for utilizing said direct current impulses for actuating the automatic switching equipment to select a desired idle outgoing toll line and: simul taneouslystore the direct current impulses onthe sender or in case the" incoming high frequency alternating current iia-puisesme intended forselec'tion of a subscriber s lineinthis exchz nge totra'i late these iinpiilses into direct currentimpulses and to utilize the direct" current" impulses for selectively" operatin-g the local' switl' l "rouunawareate-nestles- 'P lns-' mutants been illustrated by" means of the accompanying drawin s in which:

Fig; 1- showsatoll operators?cord-circuit equipped inaccoi'dancewith this invention anda jack with an associated line switch by means of which a toll operator may be automatically connected to any one'of a'plurality of common switching equipments provided for extending a toll connection.

Fig. 2 shows a portion of one of said common'switching equipments for extending a toll connection.

Fig. 3 shows another portion of the common switching equipment for the reception and translation of high frequency alternating current impulses into direct current impulses.

Fig. 4: shows a line switch used as a sender selector associated with each common switching equipment for selecting an idle sender equipment. A portion of one of these common sender equipments is is also shown in this figure, that is, equipment is shown for the reception of three digit munbers although it should be understood that senders of this type may be arranged for the reception of numbers containing a' larger number of digits.

Fig. 5 shows'another portion of the common switching equipment in which the first selector used in theextension of a toll con nection has been shown. in detail. switches whiclrmay be of'the same type have been shown diaigrammatically, it being understood that regardless of the number of the selectors that are to be employed. they are all identical in their operation with this first selector shown in detail. A portion of the terminal banks of the last selector have been shown to illustrate the grouping of the toll lines.

Fig. (3 shows a portion of a standard local switching equipment used in systems of this type for extending automatic connections to subscribers in the same exchange.

Fig. 7 shows a line switching equipment by means of which an incoming toll line may be connected through an automatic switching equipment to a toll line leading to another exchange or to a local subscriber.

Fig. 8 shows three exchanges with the principal elements of the invention indicated sc'lnnetically, particular attention being given to the arrangement of the toll lines and t'he routing'ol' the various through connections that may be made by the use of this invention.

Fig. 9 illustrateshow the various sheets may be assembled in" reading the circuits.

General description.

toll operator at tlfirou'gh' intermediate Other F operators or by automatic equipment, the number of the wanted subscriber and the exchange at which he is located, and in accordance with the general practice, the subscriber is asked to hang up his receiver until the desired connection has been established at which time the toll operator again comn'iunicates with the calling subscriber by inserting plug 12 of a cord circuit 13 into jack 11 and by calling the calling subscriber either automatically or inanually as the case may be and thus connecting the last link in the toll line connection.

In establishing a connection to the wanted subscriber, the toll operator refers to the toll code number which has been assigned to the exchange in which the wanted subscriber is located and dials this number, and upon the receipt of a signal indicating that the wanted exchange has been reached, she dials the wanted subscribers number in that exchange. The first step in establishing a toll connection on the part of the toll operator at T0, is to insert plug .14. of cord circuit 1.3 into a jack such as 1:"), it being understood that the operator is provided with a number of cord circuits such as 13 and has access to a number of jacks such as in a regular switchboard as is well known in the art. Jack 15 is associated with the brushes of an automatic switch 10 of the line switch type, the terminals of which are associated with a number of automatic switching equipments such as that shown in Figs. 2, 3, 1 and 5 and the line switch is so arranged to automatically connect with an idle equipment of this type the moment plug ll: is inserted in jack 15. As soon as a switchingequipment has been appropriated various operations take place to actuate the sender selector switch 4.10 of the saline type as line switch 16 to find an idle sender equipment such is shown at 41.0. It should be understood that a number of such equipments and senders may be provided for the use of a number of toll operators, that is, a group of senders are common to a larger group of switching equipments which in turn are common to a still larger group of jacks provided for a smaller number of operators. lVhen av sender has been appropriated, operations take place in the switching equipment to cause an impulse to be transmitted over the sleeve lead to actuate a signal in the cord circuit 13 which serves as an indication to the toll operator that dialing of the toll code number may begin.

The operator, who in the meantime has associated her common dialing equipment 1.? to the cord circuit 13 by the operation of a dialing key 19 now proceeds to dial the toll code number by operating dial 18. This common dialing equipment 1'1" is arranged to produce two types of dialing pulses sin'iultaneously such as direct current impulses alternating with high frequency alternating current. The frequency chosen in this instance for the alternating current impulses is 1000 cycles per second, but it should be understood that alternating current of other high frequencies may be used for these impulses as well as for any other high freqency alternating currents specifieally mentioned hereinafter. At this time, the 1000 cycle impulses have no effect in the establishing of a connection whereas the direct current impulses perform two distinct functions, one of these functions being to operate the sender 411 to store, as it were, thereon the toll code number, that is, the sender which includes a number of mechanically operated dials such as 4:12, 1:13 and 4-15 of the standard type used for manual operations is arranged so that each dial will be operated a number of steps equal to the number of pulses in a corresponding digit of the toll code number. The other function consists in operating a series of toll line selectors such as 505 which is shown in detail and others such as 506 and 507 shown diagrammatically but which may also be equipped to operate in response to the impulses in exactly the same manner as selector 505. hen a desired toll line, which is to form the first link .in atoll line connection has been found by the final selector 507. a signal automatically transmitted to the opposite end of the selected toll line terminating in a second exchange. This signal whichis in the form of a 1000 cycle alternating current ii'iterrupted at a 4-0 cycle rate, causes operations to take place to associate an idle automatic switching and sender equipment in the second exchange indentiral to that shown in F 2, 3, 4t, and with the selected toll line. in other words, this impulse. causes actions similar to the actions produced by the insertion. of plug 14: in jack 15 to take place, but it should be remembered that this signal is in the form of a high. frequency alternating current and when it is received at the second exchange it is caused to operate an alternating current responsive relay which is associatml with a line switch such as 71.0, and this switch is in turn caused to hunt for a connection with an idle switching equipment which in its turn actuates a line switch such as 4-10 to hunt for and connect with an idle sender such as 411. As soon as an idle sender has been found, actionstake place in these equipments at the second exchange to produce and transmit back to the originating exchange are other signal. This signal, which is in the form of a 700 cycle alternating current interrupted at a cycle rate is received through the equipment shown in Fig. '3 to cause operations to take place resulting in the release of the dials 4:12, 4.13 and *lrltlin succession. Direct current impulses represeirting the digits of the toll code number are now produced by this release of the dials and caused to operate equipment associated with the sender to transmit corresponding high frequency alternating current impulses over the seized toll line. These impulses are in the form of 1000 cycle alternating current pulses transmitted at the dialing rate.

lVhen these high frequency alternating curent impulses are received at the second exchange they are in turn received at an equipment identical to that shown in Fig. 3 and cause actions to take place which will result in the operation of the associated sender at this exchange to store the toll code number and at the same time actuate selector switches identical with the selector switches 505, 506 and 507 in this exchange to select an idle 6011* line leading to athird exchange. This toll line then forms a second link in the connection to the desired exchange.

If the route selected involves connections through a number of other intermediate exchanges and toll lines, the operations just described are repeated, that is, the impulses receiyed at succeeding exchanges seize idle equipments thereat and 700 cycle alternating current impulses interrupted at a 20 cycle rate are sent back to preceding exchanges and the toll code number is stored and retransmitted to actuate selectors in the same manner as when but a single intermediate cxchange is involved.

lVhen finally the desired exchange is reached, the toll line selectors at this ex change are operated in the same manner but instead of selecting an idle toll line leading to an exchange beyond; they are operated so that the final selector 507 will have its brushes establish contact with terminals indicating that this is the final exchange, that is, a ground is connected at these terminals which causes the switch equipment at this exchange to function as follows: First: to release the toll line selectors and disconnect them from the switching equipment. Secondc-to release the sender at this exchange and cause the toll line code number stored therein to be dissipated without havii'ig any effect. Third: to send a high frequency alternating current signal back tothecordcircuit at theorigin'ating exchange, and fourth: to cause the first of a series of selector switches at this exchange having access' to' the wanted suhscribefs line to be associated with the switching equipment. Thesignal sent back to the cord circuit is inthe form 01" a 700 cycle alternatingcurrent interrupted at a 40 cycle rate and causesthesupervisory lamp a). to become illuminated as an indication to the toll operator that the dialing oi the wanted subscribeids number in this exchange may begin.-

lVhen the toll operator receives this signal indication she immediately operates her dial 18 in accordance with the l'ocalnun'iber of the subscribers line desired and in this instance only the 1000 cycle alternating current impulses are effective over the estab lished toll line connection. The first operation of the dial at this time causes the signal lamp which was lighted as a dialing signal, to be extinguished. These 1000' cycle alternating current impulses are received in an equipment at the terminating exchange identical with that shown in Fig. 3', and cause operations to take lace through the line switch (310 to cause switches such as ($11, 612 and 613 to select the desired subseribers line at 615. The operation of these switches forms no part of this invention as their operation is well known in the art and only a suflicient portion thereof has been shown to indicate how the selection may be made and how they react in response to the dialing impulses as far as such reaction may affect the operation of the switching equipments of this invention.

lVhen the subscribers line at 615 is reached, the toll operator is notified by the lighting of the supervisory lamp 40 and the operator may now proceed to ring the wanted subscriber by operating a ringing key 20 and when the wanted subscriber answers by removing his receiver from the hook, the supervisory signal at the cord circuit is again extinguished to indicate this fact to the operator who now proceeds to set up a connection to the calling subscriber. This may be done as hereinbefore mentioned, manually or autoi'naticall'y. If the connection is set up automatically the cord circuit is manipulated so that the actuation of dial 18 establishes the connection. Conversation between the subscribers may now take place and when it is ended, the toll connection may be released by the operator removing the plugs 12 and 14 from the corresponding jacks and operation will then take place-to return all parts of the apparatus'to normal as will be more fully described hereinafter.

The advantage of lmving the toll operators simply dial the complete toll code number at one time without having to pay any attention whatsoever to any supervisory signals during the setting up of a? toll connection is readily apparent, but, in addition to" this, it is also of considerable advantageand importance, as shown by th'i'sin ve'ntion, to reduce the time of setting up toll connections Ibis-well known that itthe-toll,operator under the present practice finds, in connections extending through several exchanges, all the" toll lines between any two intermediate exchanges busy, the attempt to complete the connection over that route has to be temporarily abandoned, and a second attempt made later over the same route or over another route. This causes considerable delay and intermediate toll lines are unnecessarily tied up in such unsuccessful attempt to complete connections. This invention eliminates,to a considerable extent, these disadvantages as the wiring of the terminal banks at the selectors 505, 506 and 507 at the various exchanges may be such that several routes may be automatically selected for extending connections to a desired exchange. The first idle route may, therefore, be instantly selected and the time of completing a connection reduced to a minimum. The description of wiring scheme and arrangement of the contact banks employed to accomplish these results may, for the sake of clearness, be confined to a description of the arrangement at the selector 507, it

.being understood that the same general scheme may be applied to any one or all of the other selectors as required.

In this case then, it may be assumed that this selector has access to 100 toll lines divided into 10 groups of 10 lines each, each group of lines'leading to a different distant exchange. Referring now speeifical ly to Figs. 5 and 8, if connection between two exchanges, such as A and D, may be reached through intermediate exchanges over two different routes, one involving exchange C only and another involving, in addition to exchange C another exchange B, (not shown), the selector 507 in exchange A would first be set to hunt for an idle line in the group of lines leading to exchange C marked First group and if all of the lines in this preferred group are.

busy, the selector would automatically continue to hunt over the lines leading to exchange B marked Second group. If the first route is selected, a connection will, of course, extend directly through the exchange 0 to exchange D, whereas in the second case, a connection will extend through exchanges B and This arrangement could. naturally, be varied to suit different conditions and locations of exchanges, and the groups of lines leading to the various exchanges need not be of the same number nor need the routes be confined to but two. It is also understood that a choice of route may also be made at each exchange in accordance with this scheme of wiring by applying it to the terminal banks of the toll line selectors 505, 506 in the same manner it has been shown applied to the terminal banks of selector 507.

Detailed Description. In describing this invention in detail,

it may be of advantage to give a detailed description of the functions involved in setting up. a toll connection and completing a call between a subscriber in one exchange, such as A, and a subscriber in a distant exchange, such as D, involving a through toll connection, that is, a connection leading through an intermediate exchange, such as B. This type of connection will now be described in connection with the equipments shown in Figs. 1 to 7 which. represents the necessary equipment at one exchange and it should be understood that the equipments at the intermediate exchange B and the terminating exchange D are identical with that at the originating exchange A. rxssuming then that the operator at position TO as hereinbefore described has received the wanted subscribers number from the subscriber at 10 and has inserted plug l l in jack 15, the following circuit is completed: battery, winding of marginal relay 21, left hand winding of relay 22, makebefore'break contacts of relay 23, sleeve contacts of plug 14 and jack 15, makebeforebreak contacts of relay 2% and winding of relay 25 to ground. This circuit causes the energization of relays 22 and 25 the latter relay preparing a circuit for relay 26 as follows: battery, left hand armature and front contact of relay 25, winding of relay 26, to the brush 27 of line switch 16. If line switch 16 is connected to a busy switching equipment, such as is shown in Figs. 2, 3, 4; and 5, the circuit for relay 26 is completed from brush 27 through lead 28 to the left hand armature and front contact of relay 310 to ground, whereupon relay 26 is energized. The energization of relay 26 closes an operating circuit for the driving magnet 29 for the line switch 16 and the brushes of this switch are, therefore, advanced until an idle switching equipment is found, that is, until no ground is found on the terminal engaged by brush 2?. At this time, relay 26 deenergizes and magnet 29 is released. Upon the release of relay 26, relay 24 is operated as follows: battery, winding of relay 24, outer right hand armature and back contact of relay 26, right hand armature and front contact of relay 25 to ground. The operation of relay 24 closes an obvious circuit for relay 30 which connects the tip and ring conductors from jack 15 through to brushes 31 and 32 of the switch 16 to conductors 33 and 34 associated with the portion of the idle switching equipment shown in Fig. 2. The operation of relay 2 1- also opens the make-beforebreak contacts of the sleeve circuit to relay 25 which relay is thereby released and connects the sleeve circuit at its outer right hand armature and front contact" to the brush of the line switch 1.6 which brush is now connected to lead 36 extending to relay 210;. A circuit is, therefore, closed from battery at relay 21 through the sleeve lead, winding of relay 21 0 to. ground, causing this relay to, operate. The operation of relay 210 closes a circuit for relay 310- as follows: battery, outer right hand armature and front contact of relay 210, conductor 811, winding of relay 310 to ground. The operation of relay 310 provides a busy ground for lead 28 so that this switching equipnfent cannot be taken by any other line switch, such as 6. Th pc'atioir of relay 21 0 also closes a circuit at it, outer left hand arn'uiture and front contactfor relays2l2 and212}, as follows: battery, winding of relay and. left hand winding of relay 2l2in parallel to the outer left hand arn eture and: front contact of relay 210 to ground, Relay 2-12 provides a locking circuit for itself, as follows:

, battery, right hand winding of relay 212, inner. right hand armature and front cont-act of this relay, armature and. front contact of relay 213' to ground. The purpose of the operation of these two relays will become. a parent as the description proceeds. The operation of relay 210'also: closes a circuit through a resistance 214 in a connection from, lead 36, through the inner right hand armature. and front contact of relay 210 to conductor 415. Relay 210 also at its inner left hand arniature and front contact closes a connection from ground through its own windings, to lear'l 312 and resistance The. purpose, of these connections will be apparent as the. description proceeds, If, now, thesender selector 410 is resting, on; the terminals of a busysender 41-1, relay 21 5' will operate asfollows: battery, outer right hand armature and front contact, of, relay 2,10, outer left. hand, armature and back contact, of relay 216, outer left handarmature and. back contact of relay 217, Windingofrelay 215. conductor 416, middle. armature and;

2 back contact of relay 417,.brush418 of line switch 410, hand armature and,front contact ofrelay 41.9 to gro und. The opera tionof relay coinpletesca circuit forv motor magnet, 420. ofthe line switch 410: over the following circuit: battery, left; hand armature, and front contact of relay 215, conductor 421, winding of magnet 420, through its interrupting contactsto round, causing this magnet to operate the line switch 410 to adr'ance its bri-ishes to the. tor-urinals of an idle, sender Then, anidle. sender is reached, the ground} for brush 415% is removed and,relay 215, released, causing the motor magnet, 420 tostop. Simultaneously with-the operationof relay 215, relay 2 18 isalso operatedfroin battery at the outer righthandarmature] and frontcontact of relay. 210 so. thatupon the release of relay 2'15, a circuit is completed for relays 422 and 417. as follows: battery, windings ofthese relays in parallel, through conductor 423, right hand arnn ture and back contact of relay 215, arn'iature and front contact of relay 218, to ground, causing these relays 422 and 417 to operate. Relay 422 completes at its armatures and. front contacts, a connection between conductors 424 and 425 through brushes 42(5 and 427 and left hand windings of repeating coil 428 to battery and ground through the windingsof relay 429;

It will be, noted. that an idle sender such as4l1 is 'nowassociated, through the switching equipment shown in Fig, 2, with the operators cord circuit 15. The operator may, in the meantime,operate her dialing key 19 to the position 111arked,Toll preparatory to dialing. At-the lower contacts ofjthis key, a ground. is connected to provide an obvious operating circuit for relays 23 and 3,7. Theserelays operate and close circuits as. follows: relay closes. an 0bvious circuit for relay 38 at its left hand: armature and, front contact and at its makesuflicient current is provided to operate relay 39, which now closes a circuit. for lamp 40 as follows: battery, right hand armature and back contact of'relay 41, left hand; armature and front contact of relay 39, upper contacts of Toll dialing key 19, la1np4l), armature and back contact of relay 42, lower-closed contacts of listening key 43, to ground. Lamp 40 in lighting indicates to the toll operator that the circuit is now prepared for sending dialingimpulses.v

The operation of relay- 3? has in the meantime closed at, its upper and lower arinatures and front contacts, the following fundamental dialing circuit: battery, upper winding of relay 429, upper right hand winding of repeating coil 428-, brush 427' of switch 410, inner arn'iature and front contact of relay 4:22, C0lltlll(3t()l 424, inner left hand: armature and back contact of relay 216, inner lower armature. of. relay 21S, inner lower armature, and back contact of relay 219, conductor 33, brush 32,,lower armature and front contact of relay 30, ring contacts ofq'ack 15 and-plug 14, lower armature, and front contact of relay 237,

conductor 44, windings of retardation coil 45 in series, armature and front contact of relay 40, conductor 47, upper armature and front contact of relay 37, tip contacts of plug 14 and jack 15, upper armature and front contact of relay 30, brush 31, conductor 34, armature and back contact of relay 219, upper armature and back contact of relay 218, right hand armature and back contact of relay 216, conductor 425, brush 426 of switch 410 lower right hand winding of repeating coil 428 lower winding of relay 429 to ground. This causes the operation of relay 429 which closes an obvious circuit at its arn'iature and front contact to ground for relay 419 and the operation of this relay applies a ground to the terminal associated with brush 418 of switch 410 which is thereby made busy to other line switches searching for an idle sender. It should be noted that the lead from the switching equipment to brush 418 opened at the middle armature and back contact of relay 417 when it operated. The fundamental circuit through retardation coil and relay 429 also extends to pulsing relay 510 of toll line selector 505 from battery, left hand winding of pulsing relay 510, inner lower armature of relay 511 and inner lower armature of relay 220, through the ring and tip conductors and retardation coil 45 as previously traced and then through the winding of relay 221, upper armature and back contact of relay 220, upper armature and back contact of relay 511 and right hand winding of relay 510 to ground. Relays 51.0 and 221 operate in this circuit; relay 221 closing at its armature and back contact an obvious circuit for relay 222 which in operating closes a locking circuit for itself to ground at the armature and front contact of relay 213, whereas relay 510 closes a circuit for relay 512 as follows: battery, winding of relay 512, armature and front contact of relay 510, third lower armature and back contact of relay 511 to ground. The switching equipment of Figs. 2, fl, 4 and 5 is now ready for the reception of impulses representing the toll code number of the exchange desired and these impulses will, as hereinafter described, perform two functions. First to store the toll code number on the sender 411, and second, to select, by means of switches 505, 506 and 507 a toll line route to the desired exchange.

The operator may now move her dial 18 off normal and in so doing, closes a circuit for relay 49 as follows: battery, winding of relay 49, right hand armature and back contact of relay 50, off normal contacts 51 of dial 18 to ground. The operation of relay 49 closes an obvious circuit at its right hand armature and front contact for relay 41. The operation of relay 41, at its right hand armature and back contact opens the energizing circuit for lmap 40 which is now extinguished. The operation of relay 49 causes the fundamental circuit through retardation coil 45 to be closed through the left hand windings of repeating coil 52 at the left hand armature and front contact of relay 49. As the dial 18 returns to normal after having been set to the first digit of the toll code number, it opens for each pulse the energizing circuit for relay 40 at its pulsing contacts This circuit may be traced from battery, pulsing contacts 53, left hand armature and back contact of relay 50, winding of relay 46 to ground. Thus, on each release of relay 40, the fundamental circuit through the retardation coil 45 is opened, and relays 429 and relay 510 are therefore alternately retarded and operated in accordance with the operation of the contact 53. It should also be noted that upon the release of relay 46, the fundamental circuit is closed through the left hand windings of repeating coil '52, the right hand windings of which are connected to a 1000 cycle alternating current source 5-1. Thus an impulse of high frequency current is transmitted over the fundamental circuit after each direct current impulse, but these impulses do not perform any useful function at this time.

To trace first the storing of the toll code number on the sender 411, the release of relay 429 in response to the operation of the dial 18 has no effect on the circuit com pleted at its armature and back contact in operating relay 431, as this relay is slow to operate, but it should be noted that at the original operation of relay 429 a circuit was closed not only for relay 419 as previously stated but also for relay 435 and operating magnet 436 of the first dial mechanism 412. Upon the first release therefore of relay 429, relay 435 releases and does not again operate until at the end of the first series if impulses as it is slow to operate but quick to release. However on the first operation of relay 435 an obvious circuit for relay 440 was closed operating this relay which provided a locking circuit for itself from ground at the off-normal contacts 441 on the first step of dial 412 in response to the original operation of stepping magnet 4-36. Therefore, the release of relay 435 on the first release of relay 429 closes a circuit for relay 448 as follows: battery, winding of relay 443, right hand armature of relay 440, right hand armature and back contact of relay 485 to ground. A locking circuit is also provided for this relay to the grounded offnormal contacts 441. Therefore, relays 443 and 440 are maintained operated and relay 435 released during the setting of dial 412 in response to the impulses representing the first digit in the toll code number. The operating magnet however, responds to each operation of relay +129and causes the dial 412 to takeone step for each impulse, that is, its armature is attracted for each impulse and causes stepping pawl to engage the ratchet wheel 1-38 which isthereby ratcheted one step at a time. Dial 112, therefore, takes a position corresponding to the number of interruptions of the circuit for relay 429 which in turn represents the first digit in the toll codenumber. Relay 419 is slo-w to release and is, therefore, maintained operated between impulses. It should be noted that relay 1 12 .was also operated over an obvious circuit when contacts lell were closed to ground. The purpose of the ope 'ation ofthis relay willbecome apparent as the description proceeds.

On the return of dial 18 to normal, after the first digit has been sent, relay is released and relay 46 is again energized, causing relay r20 zllO be energized until the next digit is dialed. This last operation of relay e29 causes-the re-operation ofrelay 435 and magnet 4:36 the final operation of which thereby advances-dial 4:12 to its final point. The operation of relay 135, on the other hand, closes a circuit atits left hand armature and front contact for relay ii-H: as follows: battery, winding of relay 1, left handarmature and front contact o relay 35, left hand armature and front contact .of :relay 44:3 to ground, causing relay dell to operate. The operation of this relay opens .the pulsing lead at its outer right hand armature and back contact thus releasing relay ass and .magnet l36and extends this lead at this armature and its front contact to the relay ell-5 and stepping magnet %16 associated with dial e18 for the preparation-of this dial circuit for the reception of impulses represent ing the second digit of the toll code number. The relays associated with this dial are identical with those associated with dial 112, that is, relays 4e15, M7, i 18, 149 and 1-50 correspond to relays 41-35, 4-46, ell o *l-ll and -1 respectively. i

- .he dial 113 is, therefore, advanced in the same manner as the dial 1-12. After the operation of dial 18 in accordance with the second digit of the toll code number and when relay 1-29 is finally energized the pulsing lead from this relay is extended through relay .118 :to relay 1 and the stepping magnet 456. The third digit .is registered on dial 114s in :the same manner and the equipment for this dial is similar to that of the other dial, that is, relays e55, 157, 158 and 159 correspond to relays 1-35, 14:0, 1 18 and 14 i, respectively, of .the equipment associated with dial -i12. It should be :noted that the equipment for this dial n1 is not equipped withany relay corresponding to relay 142 or 450, as this is represented as being the last dial in the series and no further transfer of the pulsing lead is required. The toll code number is,

in this instance, considered as constituting but three digits. It should be understood that other dials may be provided in between dials i113 and l'll, in case toll code numbers containing more digits are to be dialed.

The toll code number is, therefore, new registered on sender all and the selection of an idle toll line route leading to the desired exchange will now ibedescribed. As stated, this selection will take place simultaneously with the storing ofithetoll code number on the sender all and the pulsing relay 510 therefore released and operated in accordance with the opening and closing of the fundamental circuit. The first opera tion of relay 510 closes an operating circuit for relay 512 as hereinbefore described and as relay 512 is slow to release, the first release of relay 510 on the first impulse therefore closes a circuit for the operation of relay 518 and the vertical stepping magnet as follows: battery, winding of stepping magnet 51st, winding of relay 513, inner armature and front contact of relay 512, armature and back contact of relay 510 to ground at the third lower armature and back contact of relay 511. Relay 513 is slow to release so that upon subsequent operations of relay 510, in response to the impulses, the vertical stepping magnet only is alternately operated and released and caused to advance the brushes 526 of selector 505 to the first vertical group of trunks represented by the first digit in the toll code number. .Vhen all of the impulses have been received, relay 510 is held energized for a sutlicient period to permit relay 513 to release. Upon the release of relay 513,-thc rotary magnet 517 isenergized to :hunt for an idle trunk in this vertical group. The first operation of rotary stepping magnet 517 is accomplished as follows: On the original energization of relay a circuit was closed for relay 516 as followsz.battery, winding of relay 516, of? normal contacts 515 which were closed onthe first rotary step of the selector, armature and front Contact of relay to ground at the outer armature and front contact of relay Thcreforc, on the release of relay 513, relay is maintained operated from theground at the third lower armature and back contact of relay 511 as follows: battery, winding of relay 516, 0d normal contacts 515, armature and back contact of rotary stepping magnet 517, left hand armature and front contact of relay 516 to I ground at the third armature and back contact of relay 511. This maintains relay 516 operated and provides, upon release of relay 513, a circuit for rotary stepping -1nagnet 57 as follows: battery, winding of steppingmagnet 517, right hand armature and front con tact of relay 516, make beforebreak contacts of relay to groundat the right lit] hand armature and front contact of relay 512. Rotary stepping magnet 517 now operates and advances the brushes to the first set of terminals representatingthe first trunk in the selected group. If this trunk is busy, that is, occupied by another selector switch such as 505, a ground willbe pres out on the lead 521. It should be noted that upon the operation of the rotary stepping magnet 517, the energizing circuit for relay 516 was opened at the armature and back contact of the stepping magnet 517 and upon the subsequent release of relay 516, the circuit for the stepping magnet 517 is opened at the right hand armature and front contact of relay 516. This ground on lead 521 of selector 505 will therefore, complete a new energizing circuit for relay 516 as follows: battery, winding of relay 516, off normal contacts 515, armature and back contact of rotary stepping magnet 517, lower outer armature and back contact of relay 511 to ground on lead 521. The operation of relay 516 will, therefore, again close the energizing circuit for rotary stepping magnet 517 which now advances the brushes 520 to the terminals of the second trunk and this alternate operation of relay 516 and magnet 517 is repeated until an idle trunk is found. hen an idle trunk is found, the ground on lead 521 is removed and relay 516 cannot again become energized. Therefore, no circuit for rotary stepping magnet 517 is provided at this time and the selector F comes to rest with its brushes 520 on the terminals of an idle trunk leading to a second selector such as 506. The leads of the selector 505 connected to brushes 520 will now be extended to the switching equipment shown in Fig. 2 by the operation of relay 511 over a circuit as follows: battery, winding of relay 516, off normal contacts 515, armature and, back contact of rotary stepping magnet 517, winding of relay 511, rotary busy contacts 522 to ground at the outer right hand armature and front contact of relay 232 which it should be remembered is operated at this time. This causes the operation of relay 511 and the conduc ors are extended as described. It is evident that relay 511 cannot operate until an idle trunk is found as the busy ground in lead 521 will short circuit this relay. The circuit for relay 510 is now opened at the upper armature and back contact and inner lower armature and back contact of relay 511, thereby causing the release of relay 510 and also the release of relay 512. The funoamental circuit over the tip and ring leads will, therefore, be advanced to the pulsing relay in the second selector 506 corresponding to relay 510 and'this relay will operate causing the operation of the relay correspondin to relay 512. The operation of relay w also provide a busy ground for the selected trunk by closing a connection from the ground at relay 232 to lead 521 at its lower outer armature and front contact. This second selector 506 and the third selector 507 which are identical with selector 505 will now operate in the same manner in response to the second and third digits of the toll code number.

Toll call routes.

It should be explained here how the various routes for the toll code connection may be chosen. For example, if an idle trunk in the proper group of trunks in the first selector represented by the first digit of the toll code number, is found leading to a second selector beginning the preferred route, no further action takes place in the selector 505. If, on the other hand, no trunksare found idle in this group a second route extending over the second selectors associated with another group of trunks may be selected, and in this case the rotary magnet 517 would continue hunting until an idle trunk is found in this second group. That is to say, these groups of trunks available to the first selector could lead to different groups of second selectors having access to groups of trunks leading to third selectors where the same arrangement could be made in regard to the groups of toll lines leading to exchanges any one of which may constitute the first stopping point in a route towards the terminating exchange. It should, of course, be understood that any combination of routes could be connected up over these selectors to choose from, although if an idle trunk is found in the first group of trunks to which the vertical magnet ad vanced the selector brushes, this preferred route would naturally be selected. Also, as selectors 506 and 507 are identical in operation to that of selector 505 the function of selecting the various routes available through these selectors will be the same. It is now clear how the last selector would choose an idle toll line in a preferred group. of toll lines leading to the next intermediate exchange and only in case all the toll lines in that group are busy, an idle toll line in the next available group will be chosen.

Second archangel .lVhen an idle toll line leading to a second exchange is found, the bridge across the tip and ring which is maintained by the relay in the third selector corresponding to relay 510 will be opened and thus permit therelease of relay 221 in the switching equipment shown in Fig. 2. The release of relay 221 closes a circuit for relay 238 as follows: battery, winding of relay 238, outer right hand armature and back contact of relay 22 1, right hand armature and front contact of relay 222 to ground at the arms:

. and ring leads to the outgoing toll line from ,the toll line after a short interval.

which the remainder of the circuit and connects .them instead to a source of 1000 cyclealter- -nating current interrupted .at a 10 cycle rate. The operation of relay 218 also opens an obvious energizingcircuit for the slow to release relay 22G, thereby permitting this relay to release and disconnect the 1000 cycle current interrupted at a -10 cycle rate from The release of relay closes an obvious ureuit for relay at its right hand armature and back cont; at, c: sing relay 22%- to operate contact of relay 224. to ground at the armature and front contact of relay 213.

This pulse. of high frequency signaling:

current causes the line circuit at the incoming toll line torhe conditioned for setting a call as will now he described. It, for example, a toll line identical to 525 is chosen by the selector 507, it would lead to another exchange in which. a line circuit, such the one. shown in Fig. 7, will be located. The call in. connection with the operations through the equipment ofthis second exchange. will be described, by means of'the circuit shown in Fig. 7.;and any other of the ClFCLlitSiShOWll in Figs. 2, t and 5 of course represent equipment identical to that located th second exchange. ll' -hen, therefore, this first impulse of 1000 cycle current interrupted a 40 cycle rate received over the toll line, from the originating office,the special alternating current responsive relay 711 is operated in such a manner .to open and close the energizing circuit to'ground at the contacts of this relay for relay 712 at a 4:0 cycle rate. It should be noted here that relay 711 may be of the type illustrated in the .copendin i application of H. lv". (ENeill Serial No. 526,152, filed December .31, .1921. jllelay 712 now responds in a similar manner and the alternate operation and release of relay 712 will cause the alternating current relay 713 to energize and remain operated as :as thelOOO cycle current interrupted at the 10 cyclcrateremains-on the line. i The operofrelay 714- providesa circuit for relay 715;;

asfollows: battery, winding of relay 715,

lefthand armatureand back contact of relay 716, makehefore-break contacts of relay 714 to ground. The operation of relay 715 closes a circuit froin ground, at itsleft hand arma;

crelay 723 as follows:

,tipand ringleads'of the, incoming;

ture and front contact to the armature of relay 717. It also closes a circuit for the winding" of relay 716 from ground, at the armature and back contact of relay 718, out relay 71*?) does not operate until relay 71 1: is again energized when the high frequency Hill on the line cease, at which time it opera in series with relay 715 and these relays lead up to the ground at relay 718. The operation of relay 716 provides an operating: circuit for relay 720 as follows: ha ite-1'3, right hand armature and hack (1 ct of relay 716, right hand inake-he;l'ore--hreal: contact of relay 721 and winding of relay 720 to ground. In case now that the brushes of lineswitch 710 rest on the terniir :ls of a busy circuit, such as shown in Fig; n this second excliange ground will he encoun tered on brush In this case, the opera tion of relay 220 provides a circuit for battery, left hand armature and front contact of relay 720, winding of relay 723 to ground at brush 722. llelaj. 723 operates and closes a circuit for stepping magnet 72% as follows: battery, magnet 721,,interrupting; contacts of this net, outer armature and right hand coir tau of relay 724; to ground, causing: the stepping magnet to operate and advance the brushes of relay 710 to the tcrmina s of another circuit, such as shown in Fig. 2. That is, the stepping magnet 724; will advance the switch until. relay 723 is rel ised causingthe pping magnet to deenergize. The release of relay 723 will now; provide a circuit for vrelay 7 21 as follows: battery, left and 7 hand windings .of relay 721,

inner ri hand armature, and hackv cont-act of 1" I723 togroundiat the right hand armature andifront contact ,of relay 720, causing rclay 721 to operate. The operation of rela r 1 1 or, 11 11 vf. 121 c ones a cncui 01 1c ay 42., as .1- Oln battery, llltllng of relay 72-3, contacts 725 of relay 121 to ground at the right hand armature and front contact ofrelay 720. The operationof relays 721 and 725 clos s the and other leads hereinafter through the brushes of switch switch equipment such as isshowni Under this condition, battei I fronrthe right hand armature and contact of. relay 716, through. the right han: armatureand-front contact of relay 72%. to brush 727 throughthe winding of relay to ground, causing the operation of relay 227; The operation of this relay closes a circuit-for relay 310'as follows: battery, right hand armature and front c ntact of relay fron ,227 lead 311, and windingof relay 210 to lnu and front contact of relay 310 to ground. Relay 220, the circuit of which was opened upon the energization of relay 721 is slow in releasing so that it holds the circuit for relays 721 and 725 until relay 227 and relay 310 are operated to furnish a holding ground for these relays. It should be noted also that relay 725 in operating disconnects the alternating current responsive relay 711 from the tip and ring of the line.

The operation of relay 227 *auscs the equipment at this exchange to operate in the same manner as the corresponding equipment at the originating exchange operated when the toll operator inserted plug 14 in jack 15. In other words, this first applica tion of 1000 cycle alternating current interrupted at a 4.0 cycle rate causes the sender selector 1-10 to select an idle sender and whereas in the former case, relay 210 started the operations for this purpose relay 22. starts the operation in this case, that is, battery is connected, at its .right hand armature and front contact for the operation of a relay, such as 218, to start the sender lector and ground is connected at its left hand armature and front contact to provide a leading ground corresponding to that supplied by relay 213.

lVhen therefore, the sender selector l10 in this exchange has established connection with an idle sender, ground is'connected to lead 4115 as hereinbefore described causing the operation of relay 219 over the inner right hand armature and back contact of relay 210 which, it should be noted, is not operated in this instance. The operation of relay 219 causes the operation of relay 228 as follows: battery, lower outer armature and front contact of relay 219, winding of relay 228, lead 31-1, armature and back contact of relay 315 to ground. The operation of relay 223 closes the direct current bridged across the tip and ring of the line connected to the first selector switch 505 in this second exchange and thus causes the operation of the corresponding relay 510 in this selector to prepare this circuit for he reception of the toll code number. The operation of relay 219 also disconnects the local tip and ring leads and connects the incoming tip and ring leads to a 700 cycle alternating current source interrupted at a 20 cycle rate shown at 229 connected to the armatures of relay 230. The operation of relay 219 also opens the operating circuit for relay 230 which releases after a short period of time and in this manner a short impulse of a. 700 cycle current interrupted at a 20 cycle rate is transmitted through the equipment shown in Fig. 7 over the toll line such as 525 to the originating exchange. This application of high frequency current causes operations to take place at the origi nating exchange causing the circuits ,lIl.S6I1(lor 111 to function to release the dials and transmit over the toll line to the second ere change, impulses of 1000 cycle alternating current representing the toll code number.

Originating emcliaage.

The operation of the equipment at the originating exchange and the release of sender 111 will now be described. lVhen, therefore, the 700 cycle current, interrupted at a 20 cycle rate, is received at the originating exchange, it passes over a path through the tip and ring leads of selectors 507, 506 and 505 in succession, the armatures controlled by relays 220, 218 and 219 to relay 315, through windings of transformer 318, amplifying vacuum tube 319 and rectifying vacuum tube 320 of the circuits shown in Fig. 3, ina manner well known in the art. These rectified pulses of 700 cycle current cause the operation and release of relay 315 at a rate corresponding to the rate of interruptions of the 700 cycle current, that is, at 20 cycles rate. This operation and release of relay 315 causes a 20 cycle current to be built up through relay 321 which is designed to operate on this current. The operation of this relay short circuits the winding of relay 322 over an obvious circuit, permitting this relay to release. The release of relay 322 closes a circuit for the operation of relay 231 in series with the release magnet 160 of the dial 112 in sender 4-11 and on which the first digit is stored. The circuit for this relay and magnet is as follows: battery, left hand armature and front contact of relay 1 1 1, release magnet 460, armature and front contact of relay 44-2, brush 161, inner left hand armature and front contact of relay 117, lead @162, winding of relay 231, outer left hand armature and back contact of relay 232, lead 323 to ground at the makebefore-break contacts of relay 322. Relay 231 operates and provides a locking circuit for itself to ground at its left hand armature and front contact and at the same time closes an obvious circuit for relay 232, causing this relay to operate and provide a locking circuit for itself through its inner left hand armature and front contact to ground at relay 213. Magnet 460 is there upon energized permitting dial 112 to return to normal. During its return to normal, the pulsing contacts 163 open and close the circuit through relay $64, per mitting it to release once for each impulse in the digit. The circuit for relay 164: may be traced as follows: battery, Winding of relay 4:64, pulsing contacts 163 of the dial 412, pulsing contacts 165 of dial 413 and pulsing contacts 466 of dial 41 1 to ground. Each release of relay 16 connects the 1000 cycle source 167 to the left hand windings of repeating coil 4:28 causing corresponding 71.419 releases, a circuit through the right induced impulses to be transmitted over the tip and ring leads to the outgoing toll line. lVhen the first dial has returned to normal, the ground on its off normal contacts f ll is disconnected, permitting the release of relays 4-410, 442, 443 and 14 i. Relay &2 is slow in releasing so that the equipments at the second exchange will differentiate between groups of impulses representing different digits. That is, the second dial 413 is not released until sufficient time has been given for the necessary functions to take place at the second exchange. The release of relay ll-2 transfers the ground from the left hand armature and front contact of relay 231 through its makc-before-break contacts to the release magnet 4-68, by way of the armature and front contact of relay 4.50. This magnet is now energized, permitting the second dial 413 to restore to normal and cause the transmission to the second exchange of a group of pulses representing the second digit. When the second dial is restored to normal, locking ground for relays 447, slelS,.al l9 and 450 is removed, permitting these relays to release and the ground from relay 231 is then transferred to the release magnet 469 of the last sender ll l. Impulses representing the last digit are thus transmitted from dial 414- over the line in a similar manner to the previous digits and when the ground at the off normal contact of dial 114 is removed, relays 457, ass and 459 are released. The release of relay 4:59 disconnects battery from the operating lead 462 except the battery connected through the Winding of relay L70. Relay 231 is sutit ciently marginal to release under these conditions and upon releasing closes a circuit for relay 216 as follows: battery, winding of relay 2-16, inner right hand armature and front contact of relay 232, right hand armature and back contacts of relay 231 to ground, causing relay 216 to operate which now disconnects leads 42 i and 425 of the sender selector from the tip and ring leads of the. toll line. It also disconnects at its outer left hand armature and back contact the operating lead for relay 218, thus causing the release of relay 21S and consequently relays 1-22 and 4-17. It should be noted that relay 470,111 the sender was operated the moment relay 231 was operated thus insuring'the proper functioning of the circuits associated with the last dial.

The release of the relay 122 causes the release of relay which in turn causes the operation of relay tea which may take place before the release of relay 1-19 which is slow in releasing. Relay 4-31 in turn closes a circuit to ground through its left hand arma ture and front contact and 4 through the .winding of relay 470 which relay is now held up in series with relay 131 but as relay 'llurning new to the functions at the re ceived exchange resulting from the receipt of the 1000 cycle current interrupted at the dialing rate representing the toll code numher, it should be noted that these impulses were transmitted from the secondary of repeating coil over leads 4 2i and 425, the tip and ring leads, through selectors 505, 506 and 20?, tip and ring leads of a toll line identical 5 n 525, through the equipment shown in brushes of sin itch TlO to leads 310 and 317, repez ting coil 318 and vacuum tubes 319 and 320, to relay 315 in the second exchange. ltelav operates in accordance with these amplified and rectified impulses and disconnects he ground from the winding of relay 22$ for a period equal to the duration of each pulse received. Each time relay 328 is released, the direct current path across the tip and ring leads is opened. In this manner pulsing relay 510 altcri'iatcly released and selector switch 505 caused to operate in the manner as hereinbefore described in response to the first digit and switches 506 and 507 a re similarly operated in response to the succeeding digits. Thus, these switches are caused to select and connect to a toll line in a group of toll lines leading to a distant exchange which may be the terminating exchange, that is, the exchange in which the wanted subscribers line is located. At the same time as the selection for a toll connection is being made, sender an at the second exchange is conditioned for repeating the same toll code number to the third exchange, that is, dials 4-12, 113 and all are set to the digits of the toll code munber. Now then, if an idle toll line leading to the terminating exchange is found througl switches 505, 506 and 50 7, relay 221 is released and the equipment at the second exchange, due to battery and ground being removed from the tip and ring of the toll line leading to the terminating exchange is also released. The release of this relay closes a circuit has been previously described causing the operation of relay 218. The operation of this relay connects the tip and ring leads of the outgoing line to the cycle current source at which is interrupted at 7. over the tip and ring Lil 

